The projector is configured to project an image onto a target such as a screen. There is a kind of a projector that measures a distance from the projector to the target and adjusts a focus on the image subject to being projected based on the measured distance. Further, there is another kind of a projector that takes a picture of the projected image to adjust a focus on the projected image based on the imaged picture.
Japanese Laid-Open Patent Application Publication No. 6-27431 (hereinafter referred to as “Patent Document 1”), for example, discloses a technology of adjusting a focus on a target that includes causing an active sensor to radiate the target with infrared rays and measuring a distance between the active sensor and the target based on the intensity of the received light reflected from the target.
Japanese Laid-open Patent Publication No. 2006-10945 (hereinafter referred to as “Patent Document 2”), for example, discloses a technology of adjusting autofocus that includes imaging a projected focus-specific pattern, detecting brightness differences between adjacent pixels of all the pixels of the imaged data, computing an absolute value corresponding to a sum of the brightness differences, and moving a focus lens to a position at which the sum corresponds to a maximum absolute value.
Japanese Laid-open Patent Publication No. 2005-181726 (hereinafter referred to as “Patent Document 3”), for example, discloses a technology (i.e., hill-climbing autofocus technology) of adjusting a focused focal point that includes allowing a photosensor to receive light reflected off a projected image, acquiring a high-frequency component from electric signals output from the phototectector, computing a contrast of the image signal (image data) obtained by integrating the acquired high-frequency component, and determining a position at which the computed contrast corresponds to a maximum value as the focused focal point.
In projecting an image by a projector, it may be necessary to project the image within a projectable range of a target such as a screen. Some kinds of the projectors are configured to specify a projectable range of the target and perform image processing (e.g., enlargement, reduction, and keystone correction) on an image to be projected so as to project the image within the specified projectable range.
The technology disclosed in Patent Document 1 may be capable of specifying the projectable range in the target (e.g., screen) by moving an optical axis of the infrared ray emitted from the active sensor utilizing a prism and measuring a distance from the active sensor to the target to specify an outer shape of the target.
The technologies disclosed in Patent Document 2 and Patent Document 3 may be capable of specifying the projectable range in the target by taking an image including a target (e.g., screen) and specifying an outer shape of the target based on brightness and contrast of the taken image.
However, when an obstacle such as a presenter or a desk is present between the projector and the target (e.g., screen), or when a wall is adjacent to a backside surface of the target, the technology disclosed in Patent Document 1 may be unable to specify the projectable range on the target due to errors occurred based on a signal input level of the photodetector element in the measured distance from the sensor to the target. Further, the technologies disclosed in Patent Document 2 and Patent Document 3 may be unable to specify the outer shape of the target based on the brightness and contrast, which may result in failing to specify the projectable range in the target.